1. Field of the Invention
This invention relates to a method and apparatus for controlling the start and stop timing of a strobe light emission when performing so-called pseudo-frame photography using a solid-state electronic image sensing device.
2. Description of the Related Art
When a special solid-state electronic image sensing device such as a frame interline transfer (FIT) CCD or the like is used, so called pseudo-frame photography can be performed. Though the details of pseudo-frame photography will be described later, in brief, the term refers to offsetting slightly the exposure time period of a first field and the exposure time period of a second field and setting the lengths of these two time periods to be equal. Since this technique makes it possible for the exposures of the two fields constituting a frame to be performed substantially simultaneously, there is almost no shift in the image between fields even if the subject photographed varies with time (as when the subject exhibits motion). In addition, since the exposure time is the same for both fields, the occurrence of flicker or the like is prevented. Moreover, since the read timing of the signal charge of the first field and the read timing of the signal charge of the second field are offset slightly, the signal charges of the two fields can be extracted separately, i.e., without being mixed.
When a strobe is fired in such pseudo-frame photography, the timing for firing the strobe is very difficult. The reason is that when the quantity of light reflected from a subject irradiated with strobe light differs for the first and second fields, this causes flicker to occur. It is required that the exposure by the strobe be made the same for the first and second fields constituting a frame.